Neman, Nemunas or Niemen[nb 1] is a river in Europe that rises in central Belarus and flows through Lithuania then forms the northern border of Kaliningrad Oblast, Russia's western exclave, which specifically follows its southern channel.

It flows generally west to Grodno within 12 kilometres (7.5 mi) of the Polish border, north to Kaunas, then westward again to the sea.

Its drainage basin settled in the late Quaternary to be roughly along the edge of the last glacial sheet so dates to about 25,000 to 22,000 years BC.

At its delta Nemunas splits into a maze of river branches and canals mixing with polders and wetlands and is a very attractive destination for eco-tourism.

In German road maps and lexika, only the 112-kilometer (70 mi) section within Prussia (starting at Schmalleningken) was named Memel; the bulk of the river was Niemen.

The border between the State of the Teutonic Order and Lithuania was fixed in 1422 by the Treaty of Lake Melno and remained stable for centuries.

Countless companies and organizations in Lithuania have "Nemunas" in their name, including a folklore ensemble, a weekly magazine about art and culture, a sanatorium, and numerous guest houses and hotels.

One of the most famous poems by Maironis starts: Smaller rivers and rivulets in Lithuania with names morphologically derived or cognate are the Nemunykštis, Nemuniukas, Nemunynas, Nemunėlis and Nemunaitis.

The etymology is disputed: some say that "Nemunas" is an old word meaning "a damp place",[9] while others that it is "mute, soundless river" (from nemti, nėmti "to become silent", also memelis, mimelis, mėmė "slow, worthless person").

[14] The largest cities on the river are Grodno in Belarus, Alytus and Kaunas in Lithuania, and Sovetsk in the Kaliningrad Oblast of Russia.

In Kaliningrad, industrial centers near the river include Sovetsk and Neman, which have large pulp and paper production facilities.

Fish found include the: perch, pike, zander, roach, tench, bream, rudd, ruffe, and bleak.

Its tributaries have borne stone loach, three-spined stickleback, minnows, trout, sculpins, gudgeon, dace and chub.

Environmental issues include water quality (eutrophication and pollutants largely due to outdated technology sewage treatment works), changes in the hydrological regime, and flooding control.